Heat and mass transfer in falling films technology applied to the generator and the rectifier of an ammonia-water absorption refrigeration cycle

Abstract

Powering ammonia-water absorption refrigeration cycles with solar energy demands an operating temperature above 170 ∘C for the proper generator operation when conventional flooded generator technologies are used. However, the falling film technology operates at a lower temperature due its superior heat and mass transfer performance. Therefore, an experimental investigation focused on the energy balance along with a heat and mass transfer analysis between liquid and vapor ammonia-water mixtures in the generator and the rectifier have been developed. Four experimental sets of runs were carried out for oil temperatures at 111 and 136 ∘C, strong solution mass fraction between 0.37 and 0.47, two rectification temperatures at 34 and 63 ∘C, and a strong solution mass flow rate of 0.016-0.027 kgs−1. Heat transfer rates for both components were computed by overall energy balances over the components. Moreover, the latent heat and sensible heat rate were calculated. The results indicated that the heat transfer process in the rectifier was lower for the minimum generation temperature. The maximum heat transfer coefficients for the liquid and vapor phase were respectively 5476 and 26Wm−2∘C−1. Analogously, the maximum mass transfer coefficients between the liquid film and vapor phase were 1.27·10−4 and 3.25·10−2ms−1.